System and method for controlling engagement of a clutch

ABSTRACT

A control system and method is provided for controlling engagement of a vehicle master clutch ( 16 ) in response to a throttle operating parameter. The method includes the steps of determining a throttle operating parameter value and setting an operating mode of the clutch based on the throttle operating parameter value. The method may include the steps of comparing the throttle operating parameter value to a threshold value and setting the operating mode of the clutch based on the comparison step. The control system includes a microprocessor for receiving signals corresponding to a throttle operating parameter value. The microprocessor sets an operating mode of the clutch based on the throttle operating parameter value or, optionally, the comparison of the throttle operating parameter value to a threshold value.

FIELD OF THE INVENTION

The present invention relates to clutch controls for automaticallycontrolling the engagement and disengagement of transmission masterclutches, and more particularly relates to clutch controls that controlengagement of a transmission master clutch in response to throttleapplication.

BACKGROUND OF THE INVENTION

Automatic mechanical transmission systems and the automatic controls forthe master clutches thereof are known in the prior art as may be seen byreference to U.S. Pat. Nos. 3,478,851; 3,752,284; 4,019,614; 4,038,889;4,081,065 and 4,361,061, the disclosures of which are herebyincorporated by reference.

Briefly, in such automatic mechanical transmissions systems, variousdrive line operations, including, the supply of fuel to the engine, theengagement and disengagement of the master clutch, the shifting of thetransmission and the operation of other devices, such as input or outputshaft brakes, are automatically controlled by a control system basedupon certain measured, sensed and/or calculated input parameters.Typically, the input parameters include engine speed, throttle position,transmission input and/or output shaft speed, vehicle speed, currentengaged gear ratio, application of the brakes and the like. The termthrottle position is utilized to signify the position or setting of anyoperator controlled device for controlling the supply of fuel to anengine.

Referring specifically to the automatic clutch control, in a vehicleequipped with an automatic mechanical transmission, during normaloperation, when starting from rest or operating at a very low speed, themaster friction clutch is modulated between fully disengaged and fullyengaged conditions, i.e., is partially engaged, according to certaininput parameters, to maintain the engine speed at a set value above idlespeed and/or to achieve smooth starts. This method of engaging themaster clutch generally provides a high quality and consistentengagement of the clutch under all types of throttle applications.However, a smooth and consistent engagement of the clutch is notnecessarily desirable in all circumstances, particularly when thevehicle is starting out on a steep grade or when other aggressiveperformance is demanded by the driver or the control system.

SUMMARY OF THE INVENTION

In accordance with the present invention, a clutch control system andmethod for controlling engagement of a vehicle master clutch is providedthat controls engagement of the master clutch in response to a throttleoperating parameter. The method includes the steps of determining athrottle operating parameter value and setting an operating mode of theclutch based on the throttle operating parameter value. The method mayalso include the steps of comparing the throttle operating parametervalue to a threshold value and setting the operating mode of the clutchbased on the comparison step.

In another embodiment of the invention, the method includes the steps ofdetermining at least one vehicle operating condition and comparing thevehicle operating condition to a predetermined limit. The operating modeof the clutch is then set based on the step of comparing the vehicleoperating condition to the predetermined limit.

The control system includes a microprocessor for receiving signalscorresponding to a throttle operating parameter value. Themicroprocessor sets an operating mode of the clutch based on thethrottle operating parameter value or, optionally, the comparison of thethrottle operating parameter value to a threshold value. In anotherembodiment of the invention, the microprocessor determines a vehicleoperating condition and compares the vehicle operating condition to apredetermined limit. The microprocessor sets the operating mode of theclutch based on the comparison of the vehicle operating condition to thepredetermined limit.

Various additional aspects of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration, in block diagram format, of anautomated mechanical transmission system utilizing the control systemand method of the present invention.

FIG. 2 is a schematic illustration in flow chart format of a clutchcontrol method according to one embodiment of the present invention.

FIG. 3 is a schematic illustration, in graphical format, illustratingexemplary throttle application rates and corresponding clutch engagementrates according to the control method illustrated in FIG. 2.

FIG. 4 is a schematic illustration, in graphical format, illustratingexemplary throttle application rates and corresponding clutch engagementrates according to an alternate embodiment of the present invention.

FIG. 5 is a schematic illustration in flow chart format of a clutchcontrol method according to another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, there is schematically illustrated inFIG. 1 an at least partially automated mechanical transmission system 10intended for vehicular use. The automated transmission system 10includes a fuel-controlled engine 12 (such as a diesel engine and thelike), a multiple-speed, change-gear transmission 14, and a masterclutch 16 (such as a friction master clutch) drivingly interposedbetween the engine and the input shaft 18 of the transmission.Transmission 14 may be of the compound type comprising a maintransmission section connected in series with a splitter-and/orrange-type auxiliary section. Transmissions of this type, especiallythose used with heavy-duty vehicles, typically have multiple forwardspeeds. Examples of such transmissions may be seen by reference to U.S.Pat. Nos. 5,390,561 and 5,737,978, the disclosures of which areincorporated herein by reference. A transmission output shaft 20 extendsoutwardly from transmission 14 and is drivingly connected with thevehicle drive axles 22, usually by means of a prop shaft 24.

Master clutch 16 includes a driving portion 16A connected to the enginecrankshaft/flywheel and a driven portion 16B coupled to transmissioninput shaft 18 and adapted to frictionally engage driving portion 16A.See U.S. Pat. Nos. 5,634,541, 5,450,934 and 5,908,100, which areincorporated by reference. An upshift brake 26 (also known as an inputshaft brake or inertia brake) may be used for selectively deceleratingthe rotational speed of the input shaft 18 for more rapid upshifting, asis well known.

A microprocessor-based electronic control unit (or ECU) 28 is providedfor receiving input signals 30 and for processing same in accordancewith predetermined logic rules to issue command output signals 32 tovarious system actuators and the like. Microprocessor-based controllersof this type are well known, and an example thereof may be seen byreference to U.S. Pat. No. 4,595,986, which is incorporated byreference.

System 10 includes a rotational speed sensor 34 for sensing rotationalspeed of the engine and providing an output signal (ES) indicativethereof, a rotational speed sensor 36 for sensing the rotational speedof the input shaft 18 and providing an output signal (IS) indicativethereof, a torque sensor 37 for sensing the torque of the input shaft 18and providing an output signal (IT), and a rotational speed sensor 38for sensing the rotational speed of the output shaft 20 and providing anoutput signal (OS) indicative thereof A sensor 40 is also provided forsensing a throttle pedal operating parameter and providing an outputsignal (THL) indicative thereof. A shift control console 42 may beprovided for allowing the operator to select an operating mode of thetransmission system and for providing an output signal (GR_(T))indicative thereof. System 10 also may include sensors 44 and 46 forsensing operation of the vehicle foot brake (also called service brake)and engine brakes, respectively, and for providing signals FB and EB,respectively, indicative thereof.

Master clutch 16 is controlled by a clutch actuator 50 (Autoclutch)responding to command output signals 32 from ECU 28. Alternatively, anactuator responsive to control output signals may be provided, which maybe overridden by manual operation of a clutch pedal 48. The engaged anddisengaged (i.e., “not engaged”) condition of clutch 16 may be sensed bya position sensor 16C or may be determined by comparing the speeds ofthe engine (ES) and the input shaft (IS).

Transmission 14 may include a transmission actuator 52, which respondsto output signals from the ECU 28 and/or which sends input signals tothe ECU 28 indicative of the selected position thereof. Shift mechanismsof this type, often of the so-called X-Y shifter type, are known in theprior art, as may be seen by reference to U.S. Pat. Nos. 5,305,240 and5,219,391, which are incorporated by reference. Actuator 52 may shiftthe main and/or auxiliary section of transmission 14.

Fueling of the engine is preferably controlled by an electronic enginecontroller 54, which accepts command signals from and/or provides inputsignals to the ECU 28. Preferably, engine controller 54 will communicatewith an industry standard data link DL which conforms to well-knownindustry protocols such as SAE J1922, SAE J1939 and/or ISO 11898. ECU 28may be incorporated within engine controller 54.

Additionally, ECU 28 is electrically coupled to throttle sensor 40 toreceive one or more output signals THL. Output signal THL corresponds toone or more throttle operating parameters, including, but not limitedto, throttle position, throttle application rate, and acceleration ofthrottle application. For the sake of illustration, the following methodof controlling engagement of clutch 16 will be described in response tothe throttle application rate. It will be appreciated that the inventionis not limited by the ECU 28 receiving signals from throttle sensor 40,and that the invention can be practiced by the ECU 28 receiving signalsfrom any component that is capable of detecting the desired fueling rateof engine 12, such as engine controller 54.

Referring now to FIG. 2, there is illustrated in flow chart format amethod for controlling the engagement of clutch 16 based on outputsignal THL from throttle sensor 40. Initially, the method of theinvention begins at step (S2.1). Then, ECU 28 receives an output signalTHL from throttle sensor 40 (S2.2) corresponding to a throttle operatingparameter value, e.g., the throttle application rate, and determines ifthe subject throttle operating parameter value is greater than abaseline threshold value programmed into ECU 28 (S2.3). This thresholdvalue corresponds to the “least aggressive” clutch operating mode, whichin the present embodiment, results in the highest quality clutchengagement rate. The highest quality clutch engagement rate is typicallyemployed in conventional automated mechanical transmission systems tosmoothly launch a vehicle. When the subject throttle operating parametervalue is less than or substantially equal to the baseline thresholdvalue, or in the absence of an output signal THL, ECU 28 will set clutchengagement to the least aggressive operating mode and engage clutch 16according to the highest quality engagement rate (S2.4).

If, however, the subject throttle operating parameter is greater thanthe baseline threshold value, then ECU 28 determines if the subjectthrottle operating parameter is greater than a predetermined thresholdvalue X (S2.5). If the subject throttle operating parameter value isless than the predetermined threshold value X, but greater than thebaseline threshold value, ECU 28 will engage clutch 16 according to apredetermined operating mode that is more aggressive than the leastaggressive operating mode described above (S2.6).

This process of comparing the subject throttle operating parameter valueto a threshold value and setting the operating mode of the clutchaccording to the comparison step is repeated a predetermined number oftimes until the throttle operating parameter value is compared to amaximum predetermined threshold value (S2.7). If the subject throttleoperating parameter value is less than the maximum predeterminedthreshold value, but greater than the previously compared thresholdvalue, ECU 28 will engage clutch 16 according to a predeterminedoperating mode that is more aggressive than the previous operating mode(S2.8). If, however, the subject throttle operating parameter is greaterthan the maximum threshold value, then ECU 28 will set clutch 16 to themost aggressive operating mode, which, in the present embodiment,results in clutch 16 being engaged according to the most aggressiveengagement rate (S2.9). The control method ends at step (S2.10).

Referring to FIG. 3, the method of engaging clutch 16 according to theembodiment of the invention illustrated in FIG. 2 is depictedgraphically. The top portion of FIG. 3 graphically illustrates fourexemplary throttle application rates (A, B, C and D). The bottom portionof FIG. 3 graphically illustrates four exemplary clutch engagement rates(a, b, c and d). A light application of the throttle is denoted by lineD; whereas, a heavy application of the throttle is denoted by line A.For purposes of illustration, the light application of the throttleresults in ECU 28 setting clutch 16 to the least aggressive operatingmode, which corresponds to the least aggressive clutch engagement rate(line d). In contrast, heavy application of the throttle results in ECU28 setting clutch 16 to the most aggressive operating mode, whichcorresponds to the most aggressive clutch engagement rate (line a).

Referring to FIG. 4, an alternate embodiment of the control method isdescribed. In this embodiment, the clutch operating mode is determinedas a direct function of the subject throttle operating parameter valueas the throttle pedal is depressed. Stated differently, the subjectthrottle operating parameter value is not compared to a threshold valueas described above; rather, the clutch operating mode is a directfunctional correlation of the instantaneous value of the subjectthrottle operating parameter value. This results in an infinite numberof clutch operating modes, which is in contrast to the finite number ofclutch operating modes described above and shown in FIG. 3. For example,the top portion of FIG. 4 plots four exemplary throttle applicationrates (W, X, Y and Z). The bottom portion of FIG. 4 plots four exemplaryclutch engagement rates (w, x, y and z), which are a direct functionalcorrelation of each of curves W, X, Y and Z, respectively.

Another embodiment of the present invention is shown in FIG. 5. In thisembodiment, the clutch engagement rate is modified only when ECU 28determines the need for a more aggressive engagement of clutch 16. Undercertain vehicle operating conditions it may be desirable to aggressivelyengage clutch 16, such as when the vehicle is starting on a relativelysteep grade or carrying a relatively large load, to prevent excessivewear or damage to clutch 16. In this embodiment, the method of theinvention begins at Step (S3.1). Then, ECU 28 will determine if avehicle operating condition exceeds a predetermined limit or threshold(S3.2). For example, a vehicle operating condition may be the relativeinclination of the vehicle when parked on a hill and the predeterminedlimit maybe a 10° inclination. If the subject vehicle operatingcondition is less than or substantially equal to the predeterminedlimit, then ECU 28 will set clutch engagement to the least aggressiveoperating mode described above (S3.3).

If, however, the predetermined limit is exceeded, then ECU 28 will setclutch engagement to a more aggressive operating mode (S3.4). The moreaggressive operating mode may cause ECU 28 to engage clutch 16 at afaster rate than the rate of clutch engagement prior to the moreaggressive operating mode, thereby minimizing the amount of time theclutch slips and resulting heat buildup in clutch 16. The aggressivenessof the operating mode can be determined by comparing the subjectthrottle operating parameter value to a predetermined number ofspecified threshold values, or by functionally correlating theinstantaneous clutch engagement rate with the value of the subjectthrottle operating parameter value (S3.5), both of these concepts havingbeen defined above. The control method ends at step (S3.6).

Although certain preferred embodiments of the present invention havebeen described, the invention is not limited to the illustrationsdescribed and shown herein, which are deemed to be merely illustrativeof the best modes of carrying out the invention. A person of ordinaryskill in the art will realize that certain modifications and variationswill come within the teachings of this invention and that suchvariations and modifications are within its spirit and the scope asdefined by the claims.

1. A vehicle master clutch engagement method, comprising the steps of:determining a throttle operating parameter value; and setting anoperating mode of the clutch (16) based on the throttle operatingparameter value.
 2. The method of claim 1, wherein the throttleoperating parameter value corresponds to one of throttle position,throttle application rate and acceleration of throttle application. 3.The method of claim 1, wherein the step of setting the operating mode isfurther defined by engaging clutch (16) at an increasingly aggressiverate when the throttle operating parameter value is increasing.
 4. Themethod of claim 1, further including the steps of determining at leastone vehicle operating condition, comparing the vehicle operatingcondition to a predetermined limit, and setting the operating mode ofthe clutch (16) based on the comparison step.
 5. A vehicle master clutchengagement method, comprising the steps of: determining a throttleoperating parameter value; comparing the throttle operating parametervalue to a threshold value; and setting an operating mode of the clutch(16) based on the comparison step.
 6. The method of claim 5, wherein thethrottle operating parameter value corresponds to one of throttleposition, throttle application rate and acceleration of throttleapplication.
 7. The method of claim 5, wherein the operating modecomprises engaging the clutch (16) at a least aggressive rate when thethrottle operating parameter value is less than or substantially equalto a first threshold value.
 8. The method of claim 7, wherein theoperating mode comprises engaging the clutch (16) at a faster rate thanthe least aggressive rate when the throttle operating parameter value isgreater than the first threshold value.
 9. The method of claim 5,wherein the operating mode comprises engaging the clutch (16) at a leastaggressive rate when no throttle operating parameter value isdetermined.
 10. A control system for engaging a vehicular master clutch(16) that comprises an electronic control unit (28) for receivingsignals (THL) corresponding to a throttle operating parameter value, theelectronic control unit (28) setting an operating mode of the clutch(16) based on the throttle operating parameter value.
 11. The system ofclaim 10, wherein the throttle operating parameter value corresponds toone of throttle position, throttle application rate and acceleration ofthrottle application.
 12. The system of claim 10, wherein the operatingmode comprises engaging the clutch (16) at an increasingly aggressiverate when the throttle operating parameter value is increasing.
 13. Thesystem of claim 10, wherein the electronic control unit (28) receivessignals corresponding to a vehicle operating condition, compares thevehicle operating condition to a predetermined limit, and sets theoperating mode of the clutch (16) based at least in part on thecomparison.
 14. A control system for engaging a vehicle master clutch(16), said system comprising: a processor-based controller (28); atleast one sensor (40) for sensing at least one throttle operatingparameter and providing an output signal (THL) to said controller (28)indicative thereof; and wherein the controller 28 determines a throttleoperating parameter value based on the received output signal (THL),compares the throttle operating parameter value to a threshold value,and sets an operating mode of the vehicle master clutch (16) based onthe comparison between the throttle operating parameter value and thethreshold value.
 15. The system of claim 14, wherein the throttleoperating parameter value corresponds to one of throttle position,throttle application rate and acceleration of throttle application. 16.The system of claim 14, wherein the operating mode comprises engagingthe clutch (16) at a least aggressive rate when the throttle operatingparameter value is less than or substantially equal to a first thresholdvalue.
 17. The system of claim 16, wherein the operating mode comprisesengaging the clutch (16) at a faster rate than the least aggressive ratewhen the throttle operating parameter value is greater than the firstthreshold value.
 18. The system of claim 14, wherein the operating modecomprises engaging the clutch (16) at a least aggressive rate when nothrottle operating parameter value is determined.
 19. A vehicle masterclutch engagement method for use with a vehicle that includes a fuelcontrolled engine, a master clutch and a transmission, the methodcomprising the steps of: determining a desired fueling rate of theengine; and setting an engagement rate of the clutch (16) based on thedesired fueling rate of the engine.